Pinhole grinder



lPatented Jan. "5,'221937' UNITED STATES PATENT oFFicE 2,066,586 rmnoLE GRINDER Joseph Sunnen, Kirkwood, Mo. Application, July 2s, 1934, serial 16.731.366

7 Claims.

the present invention, as well as that of the y patent aforesaid, the grinding machine comprises a mandrel which carries an abrasive stone operable in the hole -to be ground, and during the grinding operation said stone may be fed radially to take up the clearance created by the abrasive action of the stone.

In the patent mentioned the feeding of the abrasive stone is done manually from time to time as required, and when the work isto be re- -moved from the mandrel the stone is retracted manually. However, it is the object of the present invention to embody an automatic feed mechanlsm in the grinding machine which will periodically during the progress of the grinding operation cause t I, eabrasive stone to be advanced or fed into the work. This automatic feed mechariism also functions to permit the work to be released from the mandrel Without the manipulation or adjustment of any of the parts of the grinding machine.

'I'hese advantages as well" as others inherent in the invention will be better apparent from a detailed description of the same in connection with the accompanying drawings, in which:

Figure 1 is a rear elevation of my improved grinding machine showing the automatic feed mechanism forming la part thereof; Fig. 2 is a front elevation of the grinding machine showing the operating pedal for controlling the rotation of the mandrel; Fig. 3 is a side elevation of the machine showing in dotted lines a piston applied to the mandrel for the purpose of grinding the wrist pin holes; Fig. 4 is an enlarged vertical longitudinal section taken on the line 4-4 of Fig. 2 showing the normal operating position of the parts; Fig. 5 is a section similar to that shown in Fig. 4 showing the first position of the feed pulley and feed nut prior to effecting the release of the mandrel from the work; Fig. 6 is a section similar-to the sections shown in Figs. 4 and 5 showing the position'of the feed pulley and feed nut after the work has been released from the mandrel; Fig. 7 is a cross-sectional detail taken on a plane indicated by the line 1-1 in Fig. 4; Fig. 8 is a top plan of the tension adjustment control forming a part of the automatic feed mechanism; and Fig. 9 is a detail view showing the hook connection between the wedge-bar for advancing the abrasive member and the feed screw. I f

Referring to the drawings, T represents a bench or table on which the pedestal P of the grinding machine is mounted. The pedestal P carries a bracket I for supporting a motor 2 and a bracket 3 terminating at one end in a bearing 4 for the 10 .drive-shaft S.

The end of bracket 3 opposite bearing 4 is bifurcated to receive a lever arm 5 carried on'a rock shaft 6 rotatably mounted on bracket 3.

A pin 1 is mounted in the upper end of the lever 15 arm 5 and a combined pulley and friction wheel 8 is rotatably mounted on said pin. A lug 9 projects downwardly from lever arm 5, and a coiled spring Ill is connected between the lug 9 and the upper part of the pedestal P and serves to impose tension on thelever arm 5 so as to constantly urge the same to the left (Fig. 2). A second lever arm II is fixed to one end of rock shaft 6, and the free end of said lever arm II is connected by means of a rod I2 and strap I3 to an operating pedal I4, pressure upon which overcomesthe tension of the spring IIJ to move the pulley and friction wheel 8 to the right (Fig. 2).

The one end of the hollow drive-shaft S is provided with a reduced threaded extremity I5 on which is screwed -a friction wheel I6, and the opposite end of shaft S is provided with a hollow head or chuck I1 for receiving the mandrel M. 'I'he combined pulley and friction wheel 8 is driven through a belt I8 by the motor pulley I9 35 and engages thefriction wheel I6 when pressure is imposed un the pedal I4 to overcome the tension of spring I0. When the pressure is removed from the pedal I4 the tension of spring I0 rocks the lever arm 5 and disengages the friction wheel 40 8 from the friction wheel I6. The parts thus far described are in all essential respects the same as corresponding parts of my Patent No. 1,913,- 689, aforesaid, and are not herein claimed, but are described merely in order that the novel fea- 'tures to be described hereinafter may be more readily understood. l

The mandrel M is also essentially the same as the mandrel described in my Letters Patent No.

1,989,831 granted February 5, 1935, and is only 50 described herein sufficiently to enable one skilled in the art to understand the features of the present invention.

The mandrel M comprises a rod-like member 20 having a head 2l at one end and a slot 22 ex- 55 tending substantially the full length of the mandrel, including the head thereof. As described in detail in the aforesaid application, the man-l drel M is provided with integrally formed guide members 23, 23 on its periphery and has an abrasive stone 24 mounted in the slot 22, said abrasive stone being arranged for radial movement outwardly by cooperative engagement with a wedge-bar 25. The inner end of wedge-bar 25 terminates in a hook r.26 for vengagement with `a. slot 21 on the endof "the extending finger 28 forming a part of the feed screw 29 of the feed mechanism about to be described. Y

'Ihe reduced threaded extremity I5 of the driving shaft S is provided with an axially disposed bore 3D separated by a shoulder 3| from aslightly larger bore 32. An elongated nut 33 is'disposed in the bore 3i! and projects outwardly therefrom,

said nut having an enlarged portion 34, positioned .l

in bore 32 and adapted for lodgment against the shoulder -3I. The nut 33 also has' a` threaded socketv 35 open at its vinner end to receive the threaded feed screw 29, fand extends beyond the eXtremity^I5 of shaft S.- A grooved pulley 36 is fixed by a set screw 31 to the projecting end of nut .33;l arid a spring washer 38 is disposed between the p'ulley and the reduced end I5 ofthe shaft S.

A plate bracket 39 is secured to pedestal P beneath the bracketII and securely held in yplace by means of bolt 4U, which also holds the bracket I in place.' 'The bracket 39 has a. downwardly turned portion4I which is arranged adjacent to the friction wheel I6 and a lever 42 is pivotally connectedr to the center of the" bracket 4I by means of a rivet 43. Disposed on 'each side of the bracket 4I lare fibre disks 44, 44, and a second lever 45 is also' secured to the bracket 4| by means of the rivet 43 on the opposite side thereof from the 1ever42. One end of the lever 42 is bent inwardly toward the pedestal' P to form a handle 46 while the opposite end of the lever is bent to form a U-shaped terminal 41 for the purpose of straddling the friction wheel I6. The short lever 45 has its free'end traversed by a thumb screw 48, threaded stem 49 of which traverses a tapped opening 50 Jin the lever 42 adjacent to the handle 46. It is apparent that by tightening tne thumb screw 48 thelevers 42 and 45 are 'drawn together so` asto clamp between them the bracket 4I and bre disks 4,4, 44, thus holding the lever ,42 securely against movement on the pivot 43. A belt 5I is disposed over the lpulley 36 and has its ends yanchored to the extremity 41 of lever 42.

- However, ya coiled spring 52 is interposed between tudinally disposed slot 54 for receiving alug 55v projecting from one side of a disk 56 disposed Within the chuck I1. The disk 56 and a second lug 51 in opposition to .the lug 55 have a rectangular opening 58 `extending inwardly from the lugs and 51.v The head 2| of mandrel M has a slot 22 coextensive with the slot 22 in which is received the lug 51 when the mandrel is disposed within the chuck I1. A setscrew 59 traverses the chuck I1 and bears against a at face 60 formed on the end of the mandrel wherebythe same is securely held within the chuck. When the mandrel is secured within the chuck Il' the hook 26 of wedge-bar 25 is in engagement with the slot 21 on the finger 28 of the feed screw 29, said finger 28 passing through the opening 58 in the disk 56. It is apparent from the description of the parts just given that when the mandrel M is secured in the chuck I1 there can be no relative rotation between the mandrel, driving shaft S and the nger 28 of the feed screw 29.

The operation of my improved grinding machine is as follows:

We will ,assume that the piston P (shown dottedin'Fig'.,3) isrto have its wrist pin holes 6 reground for which purpose the operator has adjusted the position of the grinding stone 24 so that the mandrel may be inserted through said #wrist pin holes 0.

The operator now depresses the foot pedal I4 so as to bring the friction wheels 8 and I6 into contact, -thereby causing the spindle S and, of course, mandrel M to be rotated. He then works the piston P back and forth over the mandrel M as the-latter rotates within the wrist pin holes. If the .adjustment of the abrasive stone 2'4 is such 4that the mandrel makes but slight frictional contact with the piston pin holes the feed nut 33 will be held against rotation by the belt 5I passing over the pulley 36. However, the feed screw 29 will-of course rotate with the mandrel so the effect of holding the nut 33 against rotation is to cause the screw 29 to travel out of the threaded socket 35 of the nut. 'Ihe outward movement of the feed screw 29 and of course nger 28 is imparted to the wedge-bar 25 with the result that the stone 24 is adjusted radially outward under the influence of said wedge-bar. This outward adjustment of the stone 24 continues until the frictional contact of the stone and, of course, guide elements 23 with the walls of the piston pinholes is great enough to overcome the traction of the belt 5I on the pulley 36, whereupon said pulley is caused to rotate with the spindle S and of course mandrel M. The direction of rotation of the spindle S is as indicated by the arrow a: (Fig. 1) so that when the pulley 36 is also being rotated the lower side 5I of belt 5I is the taut side of said belt and has the spring 52 connected bet'ween its end and the end of lever 42. 'I'he effect of the spring 52 is to increase the braking effect on the pulley 36 as the frictional contact between the mandrel M and piston P increases until the resistance of the friction balances the weight of the spring 52.

This insures that the pressure between the elements 23 and 24 of the mandrel and the walls of the wrist pin holes 0 will always be the same. beyond a predetermined point the pulley 36 begins to slide on the belt 5I, preventing any further radial advancement of the abrasive stone 24. When the pressure on the elements 23 and 24 decreases the pull of the spring 52 will arrest the rotation of the pulley 36, causing the stone 24 to 'be advanced until the balance between the spring pressure 52 and the frictional resistance on the work is restored. From the foregoing it will be seen that the feed mechanism for the stone .24 operates automatically to maintain a definite frictional vresistance between the mandrel and the work.

In Fig. 4 is shown the normal operating position of the relative parts of the adjustment mechanism. It will be observed that in this operating position a clearance space is maintained between the pulley 36 and the reduced end I5 of the driving spindle S by the spring washer 318. 'I'his clearance space is important in connection Just as soon as this pressure increases 2,066,586 y:it

with the release of the work P from the mandrel when the operator desires to remove said work. Before removing the work the rotation of the spindle S and mandrel M is discontinued by relieving the pressure on the foot pedal I4, after which the operator rotates the work (and of course the mandrel M which is frictionally engaged therewith) in the direction of the dotted arrow (Fig. 1). During this rotation of the spindle S and, of course, feed screw 29, the pulley 36 is held against rotation by the upper side of the beltl which now becomes the taut side. Consequently the adjustment nut 33 is also held against rotation and the feed screw 29 draws the nut inwardly Aovercoming the pressure of the washer 38 until said washer has been flattened, as shown in Fig. 5.

At this time the clearance is now between the enlarged portion 34 of the nut 33 and the shoulder 3| in the bore 30. Up to this time the abrasive stone 24 has not moved but is still in frictional contact with the work. However, outward pressure is exerted against the pulley 36 and of course the adjustment nut 33 and feed screw 29 connected therewith by the inherent tension of the spring washer 38, which pressure suddenly becomes effective on the wedge-bar 25, pulling the same inwardly and releasing the stone 24 so that it may move radially einward out of contact with the inner surface of the work. When this action occurs the parts assume the position shown in Fig. 6 wherein it will be noticed that there is clearance between the outer surface of the stone 24 and the wrist pin hole 0.

In addition to the function of the spring 52 associated with the belt 5I, explained above, the spring 52 subserves still another function. Obviously, in a machine of this character, used by mechanicsin the shop, certain parts inevitably become oily or greasy in use. For instance, after the machine has been used 'some time, the belt 5I may become oily so that it would not ordinarily impose the same amount of friction on the pulley 36 that would be exerted were the contacting parts perfectly clean. However, the spring 52 and the taut side 5I of the belt 5| subserve to counteract any lossof elciency for the reason stated. The spring is of such weight that it will impose sufficient tension on the belt 5l to put the necessary braking effect on the pulley 36, even'though the friction has beenl reducedby the presence of lubricating oil. If, however, the maximum amount of friction exists between the belt 5I and pulley 36, the increased pull on the taut side 5|' of the belt will cause the spring 52 to stretch, in effect, lengthening the belt and lessening the contact between the belt and the pulley 36. Thus, it will be seen that the length of the belt 5I is proportional to the frictional resistance between the belt and the pulley 36. Of course, if the belt lengthens, the degree of contact between the belt and the pulley will lessen so that I have provided automatic means for maintaining the degree of contact between the belt 5| and the pulley 36 inversely proportional to the frictional resistance between the belt and the pulley. In other words, if the friction between the belt and the pulley is great, the belt is automatically loosened, and if the friction is slight, the belt retains its `maximum tautness.

Having described'my invention, I claim:

1. In combination with a mandrel having a radially adjustable abrasive element, a driving spindle for the mandrel, means movable longitudinally of the mandrel and engaging the abrasive element to eiect adjustment thereof, a feed screw connected with said means and mounted for rotation with the mandrel, an adjustment nut traversed bysaid feed screw and mounted for relative rotation in the driving spindle, a brake pulley xed to said nut, a brake belt over the pulley, an'd means associated with the belt for increasing the contact thereof with the pulley, with a decrease of frictional resistance between the `belt and the pulley.

2. In combination with a mandrel having a radially adjustable abrasive element, a driving spindle for the mandrel, means movable longitudinally of the mandrel and engaging the abrasive element to effect adjustment thereof, a feed screw. connected with said means and mounted for rotation with the mandrel, an adjustment nut traversed by said feed screw and mounted for relative rotation in the driving spindle, a brake pulley fixed to said nut, a brake belt over the pulley, and means for maintaining the degree of contact between the belt and pulley inversely proportional to the frictional resistance between the belt and the pulley.

3. In combination with a mandrel having a radially adjustable abrasive element, va driving spindle for the mandrel, means movable longitudinally of the mandrel and engaging the abrasive element to effect adjustment thereof, a feed screw connected with said means and mounted for rotation with the mandrel, an adjustment nut traversed by said feed screw and mounted foi` relative rotation in the driving spindle, a brake pulley fixed to said nut, a brake belt over the pulley, 'and expansible means in the taut side of the belt.

4. In combination with a mandrel having a radially adjustable abrasive element, a driving spindle for the mandrel, means movable longitudinally of the mandrel and engaging the abrasive element to effect adjustment thereof, a feed screw connected with said means and mounted for rotation with the mandrel, an adjustment nut traversed by said feed screw and mounted for relative rotation in the driving spindle, a pulley fixed on said adjusting nut, and a belt traversing said lpulley and anchored at its ends.

5. In combination with a mandrel having a radially adjustable abrasive element, a driving spindle for the mandrel, means movable longitudinally of the mandrel and engaging the abrasive element to effect adjustment thereof, a feed screw connected with said means and mounted for rotation with the vmandrel, an adjustment nut traversed by said feed screw and mounted for relative rotation in the driving spindle, a pulley fixed on said adjustingV nut, a belt traversing said pulley and anchored at its ends, and a spring washer interposed between said pulley and the adjacent end of the driving spindle.

6. In combination with a mandrel having a radially adjustable abrasive element, a driving spindle for the mandrel, means movable longitudinally of the mandrel and engaging the abrasive element to effect adjustment thereof, a feed screw connected with said means and mounted for rotation with the mandrel, an adjustment nut traversed by said feed screw and mounted for relative rotation in the, driving spindle, and means for imposing a braking effect on the adjustment nut to effect a differential between the rotation thereof and the rotation of the driving spindle, said braking effect being yielding for a rotation of the driving spindle in `a mven direction and non-yielding for a rotation in Ithe refor rotation with the mandrel, an adjustment nut traversed by said feed screw and mounted for relative rotation in the driving spindle, a pulley xed on said adjusting nut, a belt traversing said pulley and anchored at its ends, and 5 a. spring in the taut side of the belt .when the driving spindle is in rotation.

JOSEPH SUNNEN. 

